Question

Explain why a real image can be projected on a screen but a virtual image cannot?

Answer 1

Hint: Recall the concept of real image and virtual image. We know that virtual images cannot be focused by light rays refracted from the lens. Also, the virtual image forms behind the lens on the same side of the object.

Complete step by step answer:
To answer this question, we need to understand what a real image is and a virtual image.

We know that a real image is formed when light coming out of the lens is converged and focused on the screen to produce its image of the object. The real image can be produced by a convex lens and concave mirror. We can draw the image formed by a convex lens as shown in the figure below.

We know that virtual image is formed by back tracing the reflected rays passing through the second principal focus and optical centre of the lens. Therefore the virtual image is not real which can be projected on the screen. We know that the image formed on the same side of the object cannot be projected on the screen. In the following figure, we can observe that the image of the object is formed on the same side of the object.

In the above figure, we have shown that the virtual image formed by the convex lens. The convex lens forms virtual image only when the object is placed between the optical centre of the lens and first principle of focus.

Note:
In the above figure, we have shown the formation of real and virtual images by convex lens because both types of images can be formed using a convex lens alone. In the case of a concave lens, only virtual images can be formed as light from the concave lens after refraction from the lens diverge in all the directions. By back tracing these rays, the virtual image of the object is formed behind the lens.